Actuating arrangements of the type described are known and permit even substantial forces to be applied to relatively little space while using the known advantages of hydraulic operating cylinders, which is highly advantageous for example in the present application to a vehicle cover as a result of the conditions of space which are very restricted at least for actuating the cover. Despite all the advantages of hydraulic operating cylinders problems can arise with such actuating arrangements, particularly when for example the hydraulic pump or its motor breaks down or, as a result of an energy supply which is absent or insufficient, cannot provide the operating pressure or at least cannot provide it to an adequate extent. In this case it is generally only possible to continue the actuation manually, which is otherwise carried out hydraulically against the resistance of the hydraulic medium discharged for example by way of a pressure-relief valve or the like, which naturally requires a great deal of force.